There are eleven diseases which humans can get from ticks in North America. One is caused by a neurotoxin, one by Rickettsia, two by Ehrlichia, two by viruses, and four by bacteria. These diseases, which we will discuss here, are Tick Paralysis, Babesiosis, Rocky Mountain Spotted Fever, Human Monocytic Ehrlichiosis, Human Granulotic Ehrlichiosis, Powassan Encephalitis, Colorado Tick Fever, Lyme Disease, Tularemia, Southern Tick Associated Rash Illness, and Relapsing Fever.
When travelling or working in tick infested areas there are a few basic precautions which should be taken. Wearing long sleeved shirts with snug cuffs, long pants (preferably with snug cuffs or bloused), using a 20% or better DEET based repellent (such as 3M Ultrathon-33%, Ben’s 30 – 30%, or Sawyer’s controlled release lotions – 20%) on exposed skin, and treating clothing and bedding with a Permethrin based compound. Sawyer products offers a “shake n’ bake kit for clothing which is based upon the military treatment kit. This method of clothing treatment can last through up to 50 washings! Aerosol spray treatments are available from many manufacturers and usually last through 6 washings.
Tents, sleeping bags, hammocks, and bug netting can be treated with Permethrin sprays to minimize infestations. Permethrin is safe to use as it stays on the material and does not absorb into the body. DEET has been under scrutiny for absorption and most DEET products now available in the USA and Canada have been proven safe. A good rule is to avoid applying on your lips, in the eyes, or on open wounds.
Lately wrist bands with DEET or Permethrin in them have appeared under various brands…these The same goes for insect collars designed for use on animals, they can be harmful when worn by humans. Eating match heads will not reduce the risk of tick bites, nor will swallowing a half of a cigarette (good field treatment for intestinal worms though).
Most ticks wander around on your body for a while before finding a suitable place to set up camp. It should become a regular practice to inspect your body each day for these little hitch hikers. Most tick borne diseases are not transmitted until 24 hours have passed so quick discovery and removal is paramount. Grab a “tick buddy” and carefully inspect each other for any ticks. Use an adhesive lint roller or wrap tape around your hand (sticky side out) to remove small, hard to see ticks from your clothes. Wash your clothes regularly to remove insects and their eggs (not to mention improving insulative value).
Remove attached ticks immediately:
· Grasp the tick’s mouthparts as close to the skin as possible with fine-tipped tweezers; pull back slowly and steadily with firm force until the barbed mouthparts can be eased out of the skin. Be patient.
· DO NOT squeeze the body of the tick or apply any substance, including petroleum jelly, finger nail polish, finger nail polish remover, repellents, pesticides, or a lighted match to the tick, while it is attached. These materials or methods are either ineffective, or worse, might force more infective fluid into the bite site.
· After removal, wash the bite site and apply an antiseptic.
· Save the tick for future identification should you develop disease symptoms. Preserve the tick by placing it in a clean, dry jar (or other sturdy container) and keeping it in the freezer. You may discard the tick after about one month, as tick-borne diseases will generally display symptoms within this time period.
· If you develop flu-like illness or rashes, or otherwise feel sick after the tick bite, seek medical attention immediately. Take the tick with you to the clinic. Prompt diagnosis and treatment will likely speed your recovery and prevent lingering symptoms.
The Rogue’s Gallery
Not all ticks are guilty of disease transmission. These little mugs are the ones we really have to be on the lookout for:
Well, let’s get on with the diseases…
Neurotoxin - Tick Paralysis.
Tick paralysis is a tick-borne disease affecting both humans and other animals, and it is characterized by the sudden onset of a progressive, ascending (starting in the lower body and moving up) paralysis. Unlike other tick-borne diseases, such as Rocky Mountain spotted fever, tick paralysis is not caused by an infectious agent (pathogen) but rather, is induced by a chemical substance that attacks the nervous system (neurotoxin). This neurotoxin is secreted by the salivary glands of certain tick species as they feed. Tick paralysis is relatively rare, but it can be fatal if the attached tick is not found and removed. The majority of cases occur in children.
Although tick paralysis is associated with over 40 species of ticks worldwide, only two species are most often to blame in North America. They are Dermacentor andersoni (Rocky Mountain wood tick) in British Columbia and the northwestern United States, where the largest numbers of human cases are reported, and Dermacentor variabilis (American dog tick) in the southeastern U.S. Other species may occasionally be involved. They include: Ixodes scapularis (blacklegged tick), Ixodes pacificus (western blacklegged tick), and Amblyomma americanum (lone star tick). In Australia, Ixodes holocyclus (Australian paralysis tick) is the culprit. Additional tick species account for the sporadic cases that occur in Europe, Africa, and South America. Only adult female ticks appear to produce the toxin responsible for causing tick paralysis.
Once attached to a host (human or animal), a female tick feeds for many days in order to acquire enough blood to produce her large brood of eggs. It is during this prolonged feeding process that the female tick manufactures a paralysis-inducing toxin in her salivary glands. This chemical is then transmitted to the host in the tick’s saliva. While pathogens can proliferate and continue to cause disease in an individual long after an infective tick has been removed, tick paralysis can only occur while a tick is attached and pumping toxin into the bloodstream. Therefore, once the tick is removed, symptoms resolve and recovery is usually rapid.
Approximately five to seven days after a tick has become attached, a person begins to feel restless, weak, and irritable. Numbness begins to be experienced in the legs, then paralysis rapidly develops and moves from the lower to the upper extremities. This is followed by paralysis of the tongue and face. The most severe complications may include convulsions, respiratory failure as the muscles that control breathing become paralyzed, and death. If the offending tick is not located and removed, tick paralysis may be fatal in approximately 10-percent of cases.
There are no laboratory tests to diagnose tick paralysis. Therefore, diagnosis is based on symptoms and a history of known or likely exposure to ticks (e.g. finding an attached tick; recreational activities such as camping; living in a tick-infested area; or having pets that spend time outdoors). If a tick is found and removed, rapid improvement of symptoms confirms the diagnosis.
There are no specific treatments for tick paralysis, other than supportive care and tick removal. Tick paralysis is cured by quickly finding and removing the tick. Therefore, if exposure to ticks is a possibility, it is crucial to check the body carefully and thoroughly for an attached tick. Ticks are often attached to the head and neck where they may be concealed by hair. If breathing is impaired, oxygen therapy or mechanical ventilation may be necessary. Removing the tick removes the source of the neurotoxin, and symptoms generally improve rapidly.
Protozoa – Babesiosis
Babesiosis is a potentially severe, and sometimes rapidly fatal, tick-borne illness caused by a protozoan parasite that infects and destroys the red blood cells. Babesia microti appears to be responsible for the majority of cases of human babesiosis in the United States. It is the most common species in the eastern and Midwestern U. S. where most cases occur. Additional types of Babesia that have been associated with human disease in limited areas of the U.S., but that have not yet been designated as distinct species, are currently known only as Babesia isolate type WA1 parasites (detected on the West Coast) and Babesia isolate type MO1 (detected in Missouri). Babesia divergens is the most common species in Europe. Other Babesia species cause illness in animals.
You can get babesiosis if you are bitten by a tick that is infected with B. microti, or less commonly, another Babesia species. Protozoa in the tick’s saliva are transmitted to you while the tick is feeding. An infected tick must be attached to you for at least several hours (usually 24-48) in order for transmission to take place. Occasionally, babesiosis has also been acquired via blood transfusion from apparently healthy, but nevertheless infected, individuals.
Only certain species of ticks are capable of transmitting Babesia. There are two vectors of Babesia to humans in the United States. Ixodes scapularis, the blacklegged tick (also known as the “deer tick”), is the primary vector for Babesia in the east and Midwest, while Ixodes pacificus, the western blacklegged tick, is a presumptive vector along the West Coast. Ixodes ricinus, sometimes referred to as the sheep tick or European castor bean tick, transmits B. divergens in Europe. Simultaneous infections with both B. microti and Borrelia burgdorferi, the agent of Lyme disease, have been documented in ticks, and there is evidence that both organisms may be transmitted during a single tick bite.
Ticks become infected by feeding on an infected animal known as a reservoir host. Reservoir hosts carry Babesia parasites in their bloodstream for a prolonged period of time, thus causing ticks that feed on them to become infected. Then, when the infected tick feeds on its next host, parasites are passed on to that host and the cycle of infection continues. Rodents, especially the white-footed mouse (Peromyscus leucopus), are the reservoir hosts for B. microti, while in Europe, cattle serve as the reservoir hosts for B. divergens.
Within the United States and Canada, human babesiosis does not appear to be geographically widespread. It is difficult to assess the true prevalence of the disease because it has not been designated as a nationally reportable illness to the Centers for Disease Control and Prevention (CDC). Also, it is suspected that many cases go undiagnosed because of the lack of symptoms in many individuals. Since the first cases were recognized in California in 1966 (unknown Babesia species) and Massachusetts (Nantucket) in 1969 (Babesia microti), several hundred cases have been documented. The majority of these cases have occurred in southern New England, especially on the coastal islands of Massachusetts (Nantucket, Martha’s Vineyard), Rhode Island (Block Island), and New York (Shelter Island, Long Island). Cases have also been reported in California, Connecticut, Missouri, New Jersey, Washington, and Wisconsin.
Based on serologic (blood) studies, most infections appear to be asymptomatic. Manifestations of symptomatic disease include fever, headache, chills, sweating, muscle aches (myalgias), fatigue, nausea, vomiting, enlarged spleen and liver (sometimes resulting in jaundice), and hemolytic anemia (anemia due to the destruction of red blood cells). Symptoms usually occur 1 to 4 weeks following a tick bite, and can last for several days, weeks, or months. The disease is more severe, and sometimes fatal, in patients who are immunosuppressed (have a weakened immune system), lack a healthy spleen, or who are elderly. In some cases, parasites may continue to circulate in the blood of asymptomatic individuals for several months or even years, making transmission of babesiosis by blood transfusion a concern. Because there have been documented cases of transfusion-acquired babesiosis, the American Red Cross does not accept blood donations from anyone who has ever had babesiosis, even if they have been treated with appropriate antibiotics.
Co-infection with Lyme disease has been documented in some patients. Co-infection may complicate diagnosis and treatment, and may result in more severe illness in the individual.
Most patients do not remember a tick bite. Diagnosis is usually made by examining blood smears under a microscope and detecting Babesia within the red blood cells. Babesia appear as tetrad (cross-shaped) or ring-shaped forms, but may be very difficult to distinguish from the Plasmodium parasites that cause malaria. Therefore, a combination of diagnostic criteria may be useful. An indirect immunofluorescent antibody assay (IFA) test can be used to detect Babesia-specific antibodies in the blood. Serologic diagnosis is established by a four-fold or greater rise in the serum titer between the acute (early) phase and the convalescent (late) stage. In addition, patient blood can be inoculated into hamsters to observe resultant infection in these animals after 2 to 4 weeks. In some cases, polymerase chain reaction (PCR) may also be used to detect Babesia DNA in the blood. Because some patients may be coinfected with Lyme disease (10-25%), blood tests should also be performed for this infection. It is important to diagnose and treat both infections.
There are no standardized treatments for babesiosis. However, the following drug regimens have been found to be useful: quinine (650 mg 3 times/day) plus clindamycin (600 mg 3 times/day or 1.2 g intravenously 2 times/ day) for 7-10 days (the dosages for children are quinine 25mg/kg plus clindamycin 20-40 mg/kg, both given in 3 divided oral doses for 7 days), OR azithromycin (600 mg 1 time/day) plus atovaquone (750 mg 2 times/day) for 7-10 days (the dosages for children are azithromycin 12 mg/kg 1 time/day plus atovaquone 20 mg/kg 2 times/day, for 7-10 days). Although all of these drugs are approved, the U.S. Food and Drug Administration
currently considers clindamycin, azithromycin, and atovaquone investigational for babesiosis. Patients who exhibit only mild symptoms may require no specific therapy. Severely ill patients with a high percentage of infected red blood cells, on the other hand, may benefit from exchange transfusion (removal of the patient’s infected blood, followed by replacement with clean, donated blood). Dialysis may be required for patients with kidney failure.
Rickettsial – Rocky Mountain Spotted Fever
Rocky Mountain spotted fever (RMSF) is a serious tick-borne illness that is caused by the bacterial organism Rickettsia rickettsii. You can get RMSF if you are bitten by a tick that is infected with Rickettsia rickettsii. Bacteria in the tick’s saliva are transmitted to you while the tick is feeding. An infected tick must be attached to you for at least several hours in order for transmission to take place.
Only certain species of ticks are capable of transmitting Rickettsia rickettsii. There are two major vectors (transmitters) of R. rickettsii to humans in the United States, the American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni). The American dog tick is responsible for transmitting the majority of RMSF cases. This tick is widely distributed throughout the eastern two-thirds of the U.S., as well as in limited areas along the Pacific Coast. The Rocky Mountain wood tick is only found in the western U.S. Both tick species are very similar in appearance.
According to the Centers for Disease Control and Prevention (CDC), approximately 500 cases of RMSF have been reported annually in the United States since 1990. Although the disease was first recognized in 1896 in Idaho, and was a serious illness in the Rocky Mountain states in the early 1900s, it soon became apparent that RMSF is widely distributed throughout most of the United States. Today, the majority of cases occur in the southeastern seaboard and south central states. North Carolina and Oklahoma report the highest incidences of RMSF. R. rickettsii only exists in the western hemisphere, and outside of the U.S., RMSF has been documented in southern Canada, Central America, Mexico, and parts of South America. Closely related organisms cause other types of spotted fever illnesses in other parts of the world.
Prior to the discovery of tetracycline and chloramphenicol antibiotics in the late 1940s, approximately 30% of persons infected with R. rickettsii died. Today, despite modern advances in medical care and the availability of effective drug treatments, the disease still has a fatality rate of 3% to 5%. Severe or fatal illness is linked to advanced age, male gender, African-American race, chronic alcohol abuse, and glucose-6-phosphate dehydrogenase (G6PD) deficiency (a sex-linked condition affecting approximately 12% of the U.S. African-American male population). The majority of patients with RMSF must be hospitalized.
Following an incubation period of 5-10 days after a tick bite, symptoms usually begin suddenly and quickly worsen. Initial symptoms can include moderate to high fever, severe headache, nausea, vomiting, muscle pain, chills, and extreme exhaustion. Within 2-5 days after the onset of fever, a red spotted rash often appears, first on the extremities (wrists, forearms, ankles, soles and palms), and then quickly spreads to cover much of the body, including the face. Abdominal pain, diarrhea, and joint pain may also develop. Since R. rickettsii invade and cause the death of cells that line blood vessels throughout the body, blood leaks through tiny holes in the vessel walls into adjacent tissues. This is the process that causes the rash associated with RMSF, and which can also result in severe damage to the heart, lungs, brain, kidneys, and other major organs and organ systems. Absence, delayed appearance, or failure to detect the typical rash, especially in dark-skinned individuals, and difficulty in distinguishing this illness from other infectious and non-infectious conditions, may contribute to more severe illness due to delayed diagnosis and treatment.
There is no widely available laboratory test that provides rapid confirmation of early RMSF. Therefore, treatment decisions should be based on symptoms and should never be delayed while waiting for confirmation by laboratory results. Epidemiological clues may strengthen an early decision to administer antibiotics (e.g. history of tick bite, residence in/travel to an area where RMSF is present, or recent activity in tick habitat, etc.). A blood test known as an indirect immunofluorescence assay (IFA) is the standard test generally used by the Centers for Disease Control and Prevention (CDC) and most state public health laboratories. Blood samples taken early (acute) and late (convalescent) are necessary in order to demonstrate a fourfold rise in antibody level (titer) to R. ricketsii. Other blood findings suggestive of RMSF may include low platelet count, low sodium level, elevated liver enzyme levels, and normal white blood cell count.
Treatment should be initiated immediately when there is suspicion of RMSF and should NOT be delayed until laboratory confirmation is obtained. Prompt treatment lessens the likelihood of severe illness or death. Doxycycline (100 mg every 12 hours for adults or 4 mg/kg body weight per day in two divided doses for children under 100 lbs) is the drug of choice for patients with RMSF, including children of all ages. Therapy is continued for at least 3 days after fever subsides and there is definite evidence of improvement. Total treatment duration is generally 5 to 10 days, except in the case of severe or complicated disease, which may require longer therapy. Chloramphenicol is an alternative drug that can be used to treat RMSF. However, because of the wide range of possible side effects associated with this drug, it is usually not prescribed except for pregnant women. Doxycycline is also the drug that is used to treat different types of ehrlichiosis, tick-borne illnesses whose symptoms may be confused with RMSF.
Ehrlichia – Human Ehrlichiosis
Human ehrlichiosis is a generic term for members of a group of tick-borne diseases known collectively as the “human ehrlichioses.” Each type of human ehrlichiosis is caused by a different, but closely related, type of very small bacteria (known as ehrlichiae) in the family Anaplasmataceae. These bacteria invade, and live within, white blood cells. The ehrlichiae were once thought to be only veterinary pathogens (disease agents).
Currently, there are several recognized types of human ehrlichiosis. In the U.S., the most common types are human monocytic ehrlichiosis (HME, caused by Ehrlichia chaffeensis), and human granulocytic anaplasmosis (HGA, caused by Anaplasma phagocytophilum -- formerly known as human granulocytic ehrlichiosis, HGE). Recently, a small number of cases of HGE have also been linked to Ehrlichia ewingii, a pathogen commonly causing ehrlichiosis in dogs (canine granulocytic ehrlichiosis) and simply referred to as Ehrlichia ewingii infection. Another type of human ehrlichiosis only occurs in limited areas of Japan and Malaysia (Sennetsu fever, caused by Neorickettsia sennetsu).
Different tick species transmit (are the vectors for) different ehrlichial pathogens, and consequently most cases of ehrlichiosis are reported within the geographic distribution of their associated vector ticks. The lone star tick (Amblyomma americanum) is the vector of E. chaffeensis, as well as E. ewingii. The majority of cases of HME (and HGE caused by E. ewingii) occur in the southeastern quadrant of the U.S., the area where the lone star tick is found. The blacklegged tick (a.k.a. ‘deer tick’, Ixodes scapularis) in the eastern half of the U.S. and the western blacklegged tick (Ixodes pacificus) along the west coast are the vectors of A. phagocytophilum. These are the locations where HGA most often occurs. The vector of N. sennetsu is currently unknown, although trematodes (flatworms) are suspected.
The human ehrlichioses are recently recognized illnesses that were made nationally reportable to the Centers for Disease Control and Prevention (CDC) in 1999. From 1999-2006, over 3000 total cases of the human ehrlichioses have been reported by the CDC.
Symptoms of the human ehrlichioses begin in 1-21 (average 7) days following infection, and they resemble those of Rocky Mountain spotted fever (RMSF). Symptoms vary greatly in severity, ranging from an illness so mild that no medical treatment is sought, to a severe, life-threatening condition. The most common symptoms are fever, headache, chills, muscular aches and pains, fatigue, and malaise, but may also include nausea, vomiting, swollen glands, diarrhea, loss of appetite, cough, shortness of breath, confusion, delirium, and coma. Rash is infrequent, especially in HGA (2-5% for HGA; up to 40% for HME) and when present may resemble the spotted rash of RMSF, although it is usually less prominent and more variable in appearance. Since the bacteria invade white blood cells, the body’s immune system is adversely affected. This lessens the body’s ability to fight other infections, and complications can quickly arise. In the most severe cases, kidney or respiratory failure occurs. There have been some deaths associated with both HME and HGA, although serious outcomes have been more frequently associated with HME.
A diagnosis of ehrlichiosis is confirmed by testing blood samples for antibody titers to the different bacterial species known to cause ehrlichiosis, and by observing the bacteria in different types of white blood cells. The antibiotic doxycycline is very effective for treating all types of human ehrlichiosis. No vaccine is available. Because human ehrlichiosis can be so severe, it is very important to obtain prompt diagnosis and treatment.
Virus – Powassan Encephalitis
Powassan encephalitis is a serious, though rare, North American tick-borne illness caused by Powassan (POW) virus. POW virus is just one of many viruses that are transmitted by arthropods (known as arboviruses) such as mosquitoes and ticks. POW virus is classified as a ‘flavavirus’ and it is closely related to tick-borne encephalitis viruses found in the Eastern Hemisphere. There are other types of encephalitis viruses present in the U.S. that are transmitted by mosquitoes. They are more common than POW virus and they cause St. Louis, Lacrosse, eastern equine, and western equine encephalitis, all serious infections in humans.
POW virus was first isolated from a patient with encephalitis in 1958 in the town of Powassan, Ontario, Canada. The first recognized case of POW encephalitis in the United States occurred in New Jersey in 1970. From 1958 through 1998, 27 cases of human POW encephalitis were reported from Canada and the northeastern United States (Massachusetts, New Jersey, New York). The last case in the U.S. occurred in Massachusetts in 1994. However, during September 1999 to July 2001, 4 new cases were identified in Maine and Vermont after testing for suspected West Nile virus was negative. As surveillance for arthropod-borne viruses continues, the recognized incidence of POW encephalitis may increase.
You can get Powassan encephalitis if you are bitten by a tick that is infected with the POW virus. In North America, POW virus has been isolated from four tick species: Ixodes cookei, Ixodes marxi, Ixodes spinipalpus, and Dermacentor andersoni. Evidence of POW virus infection has been found in 38 mammal species, primarily groundhogs. Ixodes cookei commonly infests groundhogs and is suspected to be the primary vector (or transmitter) of POW virus. Unlike I. scapularis, the major vector for the bacteria that causes Lyme disease, I. cookei rarely search for hosts on vegetation. Instead, they are most often found in or near the nests or burrows of medium-sized mammals and, therefore, rarely contact and bite humans.
Like most other arthropod-borne viruses, POW virus may cause no symptoms, or only mild illness, in some individuals. However, when the virus penetrates the central nervous system (CNS), it can cause encephalitis. POW encephalitis is often associated with significant long-term illness and it has a fatality rate of 10% to 15%. Of those patients who survive, many suffer permanent brain damage. There is no vaccine or specific therapy.
When POW virus attacks the CNS, it causes cell death, inflammation and swelling within the brain (encephalitis). The membranous coverings (meninges) of the brain and spinal cord may also become inflamed (meningitis). Symptoms usually begin suddenly 7-14 days following infection, and include headache, fever, nausea and vomiting, stiff neck, and sleepiness. As the disease progresses, more severe symptoms develop, such as breathing distress, tremors, confusion, seizures, coma, paralysis, and sometimes death.
Symptoms of different arboviral infections are difficult to distinguish. Therefore, laboratory tests are necessary to confirm diagnosis. These tests are not commercially available, but testing can be performed at the Centers for Disease Control and Prevention (CDC) when requested through state public health laboratories. Blood tests that detect antibodies to POW virus are most often used. Occasionally, POW virus may also be isolated from blood, cerebrospinal fluid, or other tissue.
There are no specific treatments or medications for Powassan encephalitis. Therapy is supportive only, directed at relieving the symptoms. This includes good nursing care, administration of intravenous fluids, respiratory support (ventilator), and prevention of secondary infections (pneumonia, urinary tract, etc.). Steroids may sometimes be used to reduce swelling in the brain.
Virus – Colorado Tick Fever
Colorado tick fever (CTF), also known as Mountain tick fever or American mountain fever, is a viral disease caused by infection with the Colorado tick fever virus (CTFV), a member of the Coltivirus genera. CTF is transmitted to humans most commonly by the bite of an infected adult wood tick, and while there is no evidence of natural person-to-person transmission, rare cases of transmission by blood transfusion have been reported.
The diagnosis of persons with CTF is complicated by non-specific nature of the symptoms. Most persons experience fever, chills, headache, muscular and skeletal pain, and malaise; these signs and symptoms can be confused with other infectious and non-infectious diseases. A closely related virus, Eyach virus, transmitted by the European sheep tick, Ixodes ricinus, has been reported in parts of Western Europe.
Colorado tick fever occurs primarily in the Rocky Mountain region of the western United States as well as the Canadian provinces of British Columbia and Alberta. More than 90% of all CTF cases in the United States are reported from Colorado, Utah and Montana. The disease is most prevalent during the summer months between April and August, and is usually limited to mountainous elevations between 1,200 and 3,000 meters. Patients with CTF are most often campers and young men, who have been exposed to tick bites during outdoor recreational activities.
Clinical manifestations of CTF can range from mild to life-threatening depending on the patient's age and general health. The first symptoms of CTF usually occur 3-7 days after a tick bite, although the incubation period can be as long as 20 days. The initial symptoms of the disease often include fever, chills, headache, muscular and skeletal pain, and malaise. Other symptoms may include nausea, vomiting, stomach pain, light sensitivity and sore throat. About half of all patients experience a two-staged “saddleback” fever characterized by 2 to 3 days of acute fever followed by a brief remission of the fever, followed by a second acute fever that may be more severe than the first. A petechial (spotted) rash occurs in 5-12% of CTF cases. In rare cases, patients experience illnesses of the central nervous system (CNS) ranging from mild to encephalitis with coma and death. CNS illnesses are commonly characterized by severe headache, sensory impairment, neck stiffness and light sensitivity.
An initial diagnosis is based on the patient's signs and symptoms and confirmation depends on laboratory testing. The appearance of a saddleback fever and the absence of a hemorrhagic rash common to Rocky Mountain spotted fever are clinical indicators of CTF. Leukopenia, a decrease in the number of circulating white blood cells, is the most common laboratory finding in CTF. The immunoflourescent (IFA) staining of blood smears may be used to identify CTFV antigens, however a confirmed diagnosis can only be made using PCR (Polymerase Chain Reaction).
No specific treatment for CTF is available. Management of CTF includes treatment of fever and pain with analgesics and acetaminophen, along with standard infection control procedures. Patients infected with CTF should advise blood collection agencies of their illness prior to donation, due to the risk of transmitting CTF through blood transfusion.
Bacteria – Lyme Disease
Lyme disease is an infectious disease that often begins with a characteristic rash, and which can later involve the joints, nervous system and/or heart. It is caused by a spiral-shaped bacterium (spirochete) called Borrelia burgdorferi that is transmitted to humans or domestic animals by the bite of an infected tick. It can sometimes become severely debilitating, but is rarely, if ever, fatal.
You can get LD if you are bitten by a tick that is infected with Borrelia burgdorferi. Bacteria in the tick’s saliva are transmitted to you while the tick is feeding. An infected tick must be attached to you for at least several hours (usually 24-48) in order for transmission to take place, so prompt removal of a tick will lessen your chance of getting sick. Also, not all ticks are infected, so a tick bite does not necessarily mean that disease will follow. In addition, you cannot get LD if an infected tick is just crawling on your skin or clothing. LD bacteria are NOT transmitted from person-to-person.
Only certain species of ticks are capable of transmitting B. burgdorferi to people. There are two vectors (transmitters) of B.burgdorferi in the United States. Ixodes scapularis, the blacklegged tick (also known as the “deer tick”), is the vector for B. burgdorferi in the east and Midwest, while Ixodes pacificus, the western blacklegged tick, is the vector along the West Coast. Ixodes ricinus, known as the sheep tick or European castor bean tick, transmits B. burgdorferi as well as other Lyme disease-causing Borrelia species in Europe, while Ixodes persulcatus, the Taiga tick, is the vector in Asia. Simultaneous infections with B. burgdorferi and Babesia microti (the agent of babesiosis), and/or Anaplasma phagocytophilum (the agent of human granulocytic ehrlichiosis), have been documented in ticks, and there is evidence that two or even all three of these organisms may be transmitted during the course of a single tick bite.
Ticks become infected by feeding on the blood of an infected animal known as a reservoir host. Reservoir hosts carry Borrelia organisms in their bloodstream for a prolonged period of time, thus allowing ticks that feed on them to become infected. Rodents, especially the white-footed mouse (Peromyscus leucopus), are the reservoir hosts for B. burgdorferi.
Like most ticks, the blacklegged tick has four life stages: egg, larva, nymph and adult. After hatching from the egg in the summer, the larval tick takes a blood meal on one host animal (usually a mouse), then falls to the ground and molts to the nymphal stage. The nymph rests during the fall/winter and takes a blood meal on another host (again, usually a mouse) the following spring. The nymph then molts to the final adult stage, either male or female. The adult female takes a blood meal on a larger animal (usually a deer) and a male tick mates with her while she is feeding. When her blood meal is complete, the female falls to the ground and lays 2,000 – 3,000 eggs in a cluster in the spring. The full life cycle of the blacklegged tick takes 2 years and requires 3 different animal hosts for completion. The ticks are most numerous in wooded areas, leaf litter, high grass, weeds and brush. They are not found in trees, and they do not jump or fly. Ticks crawl up low-lying vegetation and sit quietly with their front legs extended (questing behavior) waiting for an animal or human to pass by. They attach to the fur or clothing by direct contact.
In 1975, investigation of an unusual prevalence and geographic clustering of children with arthritis-like symptoms in Lyme, Connecticut led to the discovery of this illness. It is now known that LD occurs over wide areas of the United States. The most severely affected areas are the Northeast from Massachusetts to Maryland, the upper Midwest (especially Wisconsin), and the West Coast (especially California). These are areas where blacklegged ticks are most prevalent. However, cases have been reported in 49 states and the District of Columbia, as well as in many other parts of the northern hemisphere, particularly Europe and Asia. The Centers for Disease Control and Prevention (CDC) now reports approximately 17,000 – 20,000 cases of LD within the U.S. every year, but indicates that the actual incidence is probably much higher. LD is by far the most prevalent arthropod-borne disease in the U.S.
The first symptom of LD is usually a skin rash called erythema migrans (EM) that occurs at the site of the tick bite within 3 days to one month following infection (usually 7-14 days). The tick itself may go undetected. The rash begins as a small red spot, which gradually enlarges as spirochetes spread locally in the skin. Oftentimes the lesion has partial clearing in the center so that it resembles a donut or bull’s-eye, and it usually expands to at least several inches in diameter, sometimes up to as much as 12 inches or more. It is flat, not raised. The skin rash usually has no sensation associated with it and may therefore go unnoticed, particularly if it is located on a part of the body that is difficult to see. While the rash is red in color on light skin, it may appear more like a bruise on dark-skinned individuals. Up to 40% of people with LD may not have the early skin rash. Other common early signs of LD – with or without the rash – include flu-like symptoms such as significant fatigue, headache, sore and aching muscles and joints, fever, sore throat, stiff neck and swollen glands. If left untreated, these early symptoms of LD may disappear on their own over a period of weeks; however, this does not necessarily mean that the disease has cleared up, and serious complications could arise later. On the other hand, if promptly treated with appropriate antibiotics, the skin rash and flu-like symptoms go away within days, and complications can usually be avoided.
Later symptoms of LD can begin to appear shortly after the initial symptoms or not until weeks to months later. These symptoms occur as spirochetes begin to spread via the blood stream and lymph into tissues in other parts of the body. These symptoms may include complications of the joints, the nervous system, and the heart. Rash may recur as multiple secondary lesions on parts of the body other than the bite site in about 50% of untreated people.
Symptoms in the joints occur in up to 60% of untreated people, and primarily consist of an arthritis that affects the large weight-bearing joints such as the elbow, wrist, and especially the knee. Pain, swelling or stiffness can move from joint-to-joint, and may persist for months to years.
Neurologic complications occur in 10-20% of untreated people. The most common symptoms include facial paralysis (Bell’s palsy or other cranial nerve palsies), severe headache and stiff neck (meningitis), memory problems, sleeplessness and irritability (encephalopathy), and weakness and/or pain in the chest or extremities (radiculoneuritis). These symptoms can fluctuate in severity, and may persist for weeks, months, or years.
Heart symptoms occur in 6-10% of untreated people. Electrical conduction in the heart may be affected (heart block), sometimes requiring temporary insertion of a pacemaker, and inflammation of the heart muscle (myocarditis) may occur.
Diagnosis is based primarily on recognition of the typical symptoms of LD such as the characteristic skin rash or flu-like symptoms, particularly if they occur in the spring or summertime, or if the individual has had a known exposure to ticks or tick habitat in an area of the country where the disease is known to occur. Most patients do not remember a tick bite.
Atypical cases, or cases presenting with only disseminated stage complications, can sometimes be very difficult to diagnose. In these persons, a blood test looking for antibodies to the causative bacteria is often helpful. It should be noted that early in the disease, this blood test may be negative even though infection is present. This is because it takes a while for the body to develop a detectable level of antibodies; as LD progresses, antibody levels rise and the test becomes more reliably positive.
Oral antibiotic treatment works best early in the illness, clears up infection, and often prevents later complications. Doxycycline and amoxicillin are the most effect oral antibiotics, and 3-4 weeks treatment is usually effective. Cefuroxime axetil or erythromycin can be used for persons allergic to the penicillins or tetracyclines. Some disseminated disease symptoms, especially neurologic manifestations such as meningitis, may require high dose intravenous ceftriaxone or penicillin therapy for 4 weeks or more, depending on the severity of disease. In advanced disease, treatment failures may occur and retreatment may be necessary. Even when therapy has been successful in eliminating infection, symptoms may linger for extended periods of time due to initial damage that was caused during the course of the infection
Bacteria - Tularemia
Tularemiais an infection of animals and humans caused by the bacterial organism Francisella tularensis. There are two different biovars (strains) of F. tularensis: biovar tularensis, the primary type found in North America, is highly virulent and results in serious illness, while biovar palearctica is less virulent and produces milder symptoms. Tularemia is sometimes called rabbit fever or deer fly fever. Tularemia occurs throughout North America, Europe, the former Soviet Union, China and Japan. Worldwide, there are approximately 500,000 cases per year. In the United States, tularemia is reported during every month of the year for an annual total of 100-300 cases. Typically, the highest numbers of cases occur in the Midwest, particularly in Oklahoma, Arkansas, and Missouri.
There are many routes of exposure to F. tularensis: penetration of the skin or mucous membranes (e.g., when handling the carcasses of infected animals, especially rabbits); being bitten by an infected tick or fly (especially deer flies); eating insufficiently cooked meat from infected animals (rabbit meat can remain infective even after being frozen for several years); drinking contaminated water; or by inhaling aerosolized bacteria (e.g. dust from ontaminated soil or particles from laboratory samples). F. tularensis is considered a potential bioterrorism agent because of the highly infectious nature of aerosolized organisms. Person-to-person transmission has not been reported. Ticks are the most common arthropod source of transmission, and they include the wood tick, Dermacentor andersoni, the American dog tick, D. variabilis, and the lone star tick, Amblyomma americanum. Less commonly, tularemia has been associated with the bite of the deer fly Chrysops discalis, and in Sweden, the mosquito Aedes cinereus. Flies can be infective for 14 days, and ticks throughout their lifetime.
The severity of symptoms depends on the type of infecting strain of F. tularensis, the size of the exposure dose (number of bacteria introduced), and the route of introduction (inhalation, arthropod bite, skin contact, ingestion). If left untreated, the case fatality rate can reach 5%-15%.
Symptoms vary widely and begin 1-10 days (usually 2-4) following infection. In those cases where a person becomes infected by skin contact, for example by handling an infected animal carcass, symptoms can include a slow-growing ulcer at the site where the bacteria entered the skin (oftentimes on the hand) and swollen lymph nodes. This is known as ulceroglandular infection and it is the most common form of tularemia, accounting for over 80% of cases. The ulcer begins as a red, itchy bump that slowly enlarges and then ulcerates. Occasionally, no ulcer forms and lymph node enlargement may be the only sign of infection. Those who ingest the bacteria may report a sore throat, abdominal pain, diarrhea and vomiting. If the bacteria are inhaled, a pneumonia-like illness can follow. This is usually the most damaging route of infection. However, pneumonia may also be a complication of tularemia that is acquired via any of the routes of infection. Other symptoms of tularemia may include abrupt onset of fever (sometimes high: 103-104°F), headache, chills, extreme weakness or exhaustion, muscle pain, drenching sweats, dry cough, delirium, and septicaemia (infection throughout the blood stream). The disease may resemble typhoid fever.
Tularemia should be considered as a possibility for any patient who has an unexplained fever and has had recent exposure to ticks, biting flies, rabbits, or animal tissue in a geographic area where the disease is known to exist. Diagnosis is usually made based on clinical symptoms and supported by blood tests that show a rising antibody titer to F. tularensis. Blood tests usually become positive during the second week of illness. The blood of patients with brucellosis may cross-react with F. tularensis antigens, causing a false positive result; however, antibody titers are usually much lower for brucellosis infections than for tularemia. Isolation of the organism from an ulcer, lymph node, or sputum is confirmatory for tularemia, but this is not routinely attempted due to the danger of exposure for laboratory personnel. In addition, biopsy of infected lymph nodes must be performed with extreme care because of the likelihood for inducing septicemia in the patient as a result of bacteria released during the procedure.
Streptomycin is the treatment drug of choice. Gentamicin is also effective. Therapy should continue for at least 7-14 days. Tetracycline and chloramphenicol may also be used, but relapses occasionally occur. F. tularensis is also susceptible to 3rd generation cephalosporins (cefotaxime or ceftriaxone). When diagnosis is initially unclear, but tularemia is suspected, these cephalosporins may be administered in combination with streptomycin or gentamicin. Highly virulent organisms that are resistant to streptomycin have been reported.
One episode of tularemia generally confers long-term immunity; however, reinfection has been reported.
Bacteria - Tick-borne Relapsing Fever (TBRF)
Relapsing fever is an illness that is caused by certain bacteria in the genus Borrelia. In tick-borne relapsing fever (TBRF), as the name suggests, the Borrelia are transmitted to people via the bite of ticks. In epidemic louse-borne relapsing fever (LBRF), also known as typhus fever, the disease is spread by lice. LBRF is not found in the United States. TBRF occurs in limited areas of several western states (USA), western Canada, and a number of other countries throughout the world. TBRF is not spread from person-to-person.
The ticks that transmit TBRF Borrelia are argasid (soft) ticks of the genus Ornithodoros. Soft ticks are different from the ixodid (hard) ticks that transmit more common diseases such as Lyme disease, Rocky Mountain spotted fever, and human ehrlichiosis. Each species of Ornithodorus tick is the vector for (carries and transmits) a different species of TBRF Borrelia, and in each case the species of Borrelia is named after the tick. For example, most cases of TBRF in the United States are caused by Borrelia hermsii, which is transmitted by the bite of Ornithodoros hermsi. In Texas, O. turicata transmits B. turicatae. Likewise, several other Ornithodoros tick species transmit associated TBRF Borrelia bacteria in other parts of the world.
Most people become infected while vacationing during the summer months. Ornithodoros hermsii ticks are found in rural areas that are usually mountainous and forested. They live in dark, cool places where rodents nest, such as woodpiles outside buildings, in house crawl spaces, or between walls or beneath floorboards inside rustic cabins. In Texas, O. turicatae ticks are found in caves. If rodents are scarce, Ornithodoros ticks may bite humans that are nearby. The ticks usually feed at night, typically while people are asleep, and they remain attached for only a short time (15 - 30 minutes). If the ticks are infected, they pass on infection during the brief tick bite. The bites are painless and most people never realize they have been bitten.
Ornithodoros ticks can become infected with Borrelia in two ways. The first way is by feeding on an infected animal known as a reservoir host. A reservoir host can carry Borrelia in its bloodstream for a prolonged period of time, thus causing ticks that feed on it to become infected. Then, when the infected tick feeds on its next victim (host), the bacteria are passed on to that individual or animal. Rodents, including deer mice, squirrels, and chipmunks are the primary reservoir hosts for B. hermsii. The second way a tick can become infected is by a process called transovarial transmission. In transovarial transmission, an infected adult female Ornithodoros tick passes on the Borrelia directly through her eggs to the next generation of ticks. Ornithodoros ticks can live for up to 10 years or more, and they remain infective for the duration of their lifespan.
TBRF has been documented in limited areas of 11 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Texas, Utah, Washington, and Wyoming), although the majority of cases have been reported from California and Washington. TBRF frequently occurs in small clusters or multi-case outbreaks, often among groups of people who share a rustic facility that is infested with rodents. Two such outbreaks occurred in 2002: Montana (5 cases – 1st demonstration of TBRF and the tick in this state) and New Mexico (11 cases). During 1990-2000, a total of 247 cases were reported from western U.S. states, but the number of cases is undoubtedly underreported. One reason for lack of reporting may be misdiagnosis, since travelers who are infected may return home to areas where physicians are not familiar with the disease. In addition, the disease is not nationally notifiable to the Centers for Disease Control and Prevention (CDC), although many western state and local health departments do require reporting within their jurisdictions.
Most people who are infected get sick about a week after they are bitten by the tick. The symptoms include repeating bouts of fever, chills, headache, muscle or joint aches, and nausea that last from 2 - 7 days, punctuated by periods of apparent wellness that last for about a week. The initial symptoms are the most severe, with sudden onset of high fever and severe headache. A spotted and/or itchy rash may sometimes occur during this first episode of illness. The number of episodes or “relapses” ranges from 2 - 10, and each is less severe than the previous one. Serious complications or death (fatality rate of 0 - 10%) can occur if the illness is not treated, especially in the very young, elderly, pregnant, or debilitated.
Recurring fever is suggestive of TBRF. TBRF is confirmed by blood culture or observation of Borrelia bacteria in a blood smear obtained from the patient during an episode of fever. If these tests are unavailable or inconclusive, serological testing of paired acute and convalescent samples for antibody titers can be performed by the CDC.
Infection is usually cleared up easily with a 7 - 14 day regimen of antibiotic therapy. The tetracyclines or penicillins, or alternatively erythromycin, are the drugs of choice for treatment of TBRF. Within 1 - 4 hours of initiation of treatment, a temporary Jarisch-Herxheimer reaction (a worsening of symptoms) is common. This condition should be monitored closely, as it can become serious if not managed properly.
Bacteria - STARI
Southern tick-associated rash illness (STARI) is the name that the Centers for Disease Control and Prevention (CDC) has given to a newly recognized tick-transmitted disease that produces a rash similar to, and often indistinguishable from, the rash caused by Lyme disease (erythema migrans). STARI occurs primarily in the southeastern and south-central United States and is sometimes referred to as “Lyme-like illness.” STARI is not yet well-defined.
Unlike Lyme disease, which is transmitted by the bite of Ixodes scapularis (blacklegged tick, also known as the “deer tick”), STARI is associated with the bite of the lone star tick, Amblyomma americanum. The lone star tick is common in the southeast and southcentral United States, the same geographic location where most cases of STARI occur. Spiral-shaped bacteria known as spirochetes have been detected in a small percentage (1-5%) of the A. americanum ticks collected from this region. DNA analysis of the spirochetes has indicated that they are not Borrelia burgdorferi, the agent of Lyme disease, but are a different, newly recognized species, Borrelia lonestari. You may get STARI if you are bitten by a lone star tick that is infected with B. lonestari.
In 2001, a patient from New York developed a rash indistinguishable from erythema migrans (the hallmark rash of Lyme disease) at the site of a lone star tick bite. The patient had been traveling in both Maryland and North Carolina prior to noticing the attached tick. Blood testing for Lyme disease was negative. DNA testing of both the tick and a biopsy of the rash showed evidence of B. lonestari. This is a strong indication that B. lonestari causes STARI, and that A. americanum is a capable vector (transmitter) of the pathogen.
The current incidence of STARI is unknown. A case definition has not yet been developed, so the disease is not nationally reportable. The CDC is continuing to study the illness in order to more clearly define it.
Persons experiencing an expanding red, ring-like rash with central clearing (erythema migrans) following the bite of a lone star tick, Amblyomma americanum, or following exposure to ticks even if there is not a known tick bite, especially those living or traveling in southeastern or south-central states, should see a physician. A mild illness characterized by symptoms such as fatigue, headache, stiff neck, and occasionally fever, or other generalized symptoms may accompany the rash.
There is currently no specific diagnostic test for STARI. The CDC is interested in obtaining samples from patients who have suspected STARI so that further research can be conducted. Evidence to support a clinical suspicion of STARI include rash, other suggestive symptoms, recent travel history to the southeast or south-central United States, known lone star tick bite, activities they may have resulted in tick exposure, and diagnostic tests that rule out traditional Lyme disease. In addition, DNA tests of skin and/or blood specimens may be possible if submitted to the CDC.
There are currently no specific recommendations for treating STARI. However, in most published case reports to date, the rash and other accompanying symptoms resolved quickly after the initiation of doxycycline therapy.
What is the likelihood of getting one of these diseases??
Statistical reporting has not yet been compiled for many of these diseases, but the following excel files from the US CDC shows reported cases of Lyme disease, Rocky Mountain Spotted Fever, and Human Ehrlichiosis.
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